NMR spectroscopy is a non-destructive technique used to analyze the structure of a molecule by exploring its electronic orientation. This article examines the advantages and limitations involved in the application of NMR spectroscopy and provides an overview of its industrial application.
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NMR spectroscopy is a widely used analytical tool in industrial and academic settings. This method provides information on the molecular structure at the atomic level and is a promising tool for analyzing molecular dynamics and interactions at the atomic level.
It is a radiofrequency spectroscopy technique involving the electromagnetic manipulation of the nuclear spin. Although several nuclei in the periodic table are NMR-active, commonly studied nuclei include isotopes of carbon (13C), hydrogen (1H), nitrogen (15N), phosphorus (31P), sodium (23Na), and fluorine (19F).
Compared to other spectroscopic techniques that can reveal the structural information of a molecule, NMR spectroscopy helps in the complete analysis of the chemical structure through a highly informative spectrum, revealing intramolecular interactions.
Advantages of NMR Spectroscopy
In NMR spectroscopy, when a sample is exposed to an external magnetic field, the nuclei of the atoms are excited and emit resonant frequencies that are recorded, converted, and analyzed. This technique offers several advantages.
- As a non-destructive and non-invasive technique that provides molecular dynamics and interactions in a molecule, it helps retain liquid or solid samples for future studies.
- Samples being analyzed by NMR spectroscopy do not require sample preparation except dissolving in suitable deuterated solvents.
- NMR spectroscopy helps obtain accurate three-dimensional (3D) structural information from molecular vibrations within the natural environment, keeping the sample intact.
- NMR spectroscopy facilitates the simple and rapid acquisition and analysis of data.
- The latest developments in NMR instruments have allowed the measurement of self-diffusion coefficients and extraction of physical data from samples.
Limitations of NMR Spectroscopy
Despite its robustness as an analytical tool, NMR spectroscopy has a few limitations.
- A common limitation is the low sensitivity of NMR instruments to insufficient sample concentrations, which leads to poor spectra. The low sensitivity of the instrument is due to the weak interaction energies of the NMR magnetic resonance with the sample molecules.
- NMR instruments and their maintenance are expensive because they require large and powerful magnets as energy sources and cryogenic liquids for cooling.
- NMR spectroscopy does not support the analysis of higher molecular weight molecules because of the complexity and difficulty in interpreting the spectra.
- Molecules with ionic states cannot be studied by NMR spectroscopy.
- It is difficult to resolve hydrogen atoms with similar resonant frequencies within a molecule.
- Only nuclei with magnetic moments can be analyzed.
Industrial Applications of NMR Spectroscopy
Among a myriad of analytical techniques available for a scientist, NMR spectroscopy provides the most usable data in a wide range of fields:
Chemistry Laboratories: Researchers in chemistry rely heavily on NMR spectroscopy to analyze and confirm molecular structures of simple and complex molecules. Recently, benchtop NMR spectrometers that utilize permanent magnets have been replaced as cost-effective alternatives to conventional high-field NMR spectrometers in laboratories.
Food Industries: Low-field NMR spectroscopy is used in the food processing industry as a non-invasive, rapid, sensitive, and cost-effective analytical method. NMR spectroscopy can provide timely information on quality parameters during food processing.
NMR spectroscopy has also been used to identify carotenoids, profile amino acids, map protein structures, and quantify metabolites in food products before they hit the market.
Drug Discovery and Development: In addition to providing 3D structural information at the atomic level, the application of quantitative NMR spectroscopy is crucial for the selection of lead compounds with desirable absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties.
Magnetic Resonance Imaging (MRI): MRI utilizes the magnetic field and radio frequency of NMR to visualize soft tissues with high sensitivity, spatial resolution, and contrast. It is used as a diagnostic tool for many pathological conditions.
Cancer Diagnosis: NMR spectroscopic techniques are used for the fast and accurate analysis of tissues, cell extracts, biological fluids, and others. This technique helps to obtain biochemical information at the molecular level, which is crucial for tumor research.
Latest Advances in NMR Spectroscopy
An article recently published in Pure and Applied Chemistry reported a novel approach for obtaining the 1H NMR spectra of alcohols on a large bore using a Carr–Purcell–Meiboom–Gill (CPMG) sequence with multi-echo data. The obtained data had a high signal-to-noise ratio, which matched that of the computer simulations.
Another article published in Animals reported a study on the clinical setting of mastitis that compared multiple biological specimens of animals using 1H-NMR spectroscopy. The results revealed the presence of 23 molecules common across biological fluids. Integrating these results revealed that clinical mastitis affects various biological pathways.
Overall, NMR spectroscopy is a powerful analytical technique that is widely used in many industries. It is a promising tool that helps in the structural analysis of simple-to-complex molecules at the molecular level in a non-destructive manner.
The high sensitivity of NMR spectroscopy enables the analysis of molecules even in minute quantities, providing information on molecular environments. In addition, qNMR is a versatile analytical technique for determining the concentrations and reaction kinetics.
Despite the remarkable advantages of NMR spectroscopy, certain limitations exist, including high cost and maintenance and limited sensitivity towards complex molecules that need to be addressed by researchers to enable future breakthroughs.
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References and Further Reading
Chen, D., Wang, Z., Guo, D., Orekhov, V., Qu, X. (2020). Review and Prospect: Deep Learning in Nuclear Magnetic Resonance Spectroscopy. Chemistry - A European Journal. 26, 10391.
Edwards, J. C. (2011). A review of applications of NMR spectroscopy in the petroleum industry. Spectroscopic Analysis of Petroleum Products and Lubricants, 16, 423.
What Are the Advantages of NMR Spectroscopy? [Online] Available at https://www.labmate-online.com/news/mass-spectrometry-and-spectroscopy/41/breaking-news/what-are-the-advantages-of-nmr-spectroscopy/56559 (Accessed on 23 July 2023).
Nuclear Magnetic Resonance Spectroscopy. [Online] Available at https://conductscience.com/nuclear-magnetic-resonance-spectroscopy/ (Accessed on 23 July 2023).
NMR Spectroscopy for Chemical Industry. [Online] Available at https://www.azom.com/article.aspx?ArticleID=22501#:~:text=A%20popular%20application%20for%20benchtop,quality%20of%20incoming%20raw%20materials (Accessed on 23 July 2023).
Li T, Deng P. (2016). Nuclear Magnetic Resonance technique in tumor metabolism. Genes & Diseases, 13, 4 (1), 28-36.
Zloh, M. (2019). NMR spectroscopy in drug discovery and development: Evaluation of physico-chemical properties. ADMET and DMPK, 7(4), 242-251. doi: 10.5599/admet.737
Ronen, I., Webb, A. G. (2023). 1H NMR spectroscopy of strongly J-coupled alcohols acquired at 50 mT (2 MHz) using a Carr–Purcell–Meiboom–Gill echo technique. Pure and Applied Chemistry. https://doi.org/10.1515/pac-2023-0102
Zhu, C. et al. (2023). Metabolomic analysis of multiple biological specimens (feces, serum, and urine) by 1H-NMR spectroscopy from dairy cows with clinical mastitis. Animals, 13(4), 741. https://doi.org/10.3390/ani13040741